1. Field of the invention
The present invention relates to the field of internal combustion engines for aviation and industrial purposes, and particularly but not exclusively to the field of aircraft gas turbines such as the turbine engines that are fitted to helicopters.
More particularly, the invention relates to internal combustion engines such as, for example, gas turbines that include an air inlet and that are to be used under conditions in which ice can form in the air inlet, in particular on a protective grid that is placed in said air inlet and that has the function of preventing foreign bodies from penetrating into the engine.
2. Description of the Related Art
It is well known that under certain meteorological conditions, ice can form in the air inlet of a gas turbine in such quantities that the accumulated ice can cause the air inlet of the gas turbine to become partially obstructed, possibly causing the gas turbine to be damaged totally or in part.
With helicopters, this icing phenomenon may appear in particular when the helicopter is operating in an atmosphere that is cold with humidity that is high, for example over mountains or close to an expanse of water.
It will readily be understood that the existence of a risk of icing constrains the aircraft to remain on the ground in order to avoid any risk of losing power, or of the engine stopping in flight.
The present invention thus relates to a de-icer device for de-icing an air inlet of an internal combustion engine, such as a gas turbine forming part of a helicopter turbine engine, for example.
Amongst already-known de-icer devices, mention can be made of those that use compressed air taken from the outlet of a compression stage of the gas turbine for the purpose of melting the ice.
In such devices, air under pressure is taken from the outlet of the compression stage to the air inlet in order to heat the zones of the engine that need to be de-iced, e.g. stationary members such as the air inlet ducts of the engine or indeed moving members such as the pre-rotation blades that are generally fitted with hinges and that are located immediately upstream from the compressor wheel. A major drawback of such devices is that they consume particularly large amounts of energy since they take off a significant fraction of the energy needed by the thermodynamic cycle of the engine, such as a gas turbine, thereby greatly penalizing the overall efficiency of the engine and the maximum level of power available therefrom. This form of energy take off is also not very effective since the heating operation involves undesirable cooling as a result of the air expanding in the zone concerned.
When the engine is a gas turbine, another drawback is that de-icing is not possible when the gas turbine is idling, since the compression then does not deliver sufficient air at pressure, temperature, and flow rate that enable de-icing to be performed. Under such circumstances, it will thus be understood that the operation of de-icing is poorly effective during approach stages in preparation for landing and during a landing stage itself.